Prior devices have been known for fogging fruit trees to eliminate various pests, using a tarp or covering over the fruit tree and evaporating certain pesticides, such as hydrocyanic acid as in U.S. Pat. Nos. 1,529,785 and 1,614,015 and ammonia carbon monoxide as in U.S. Pat. No. 1,938,588, and transmitting the vaporized lethal pesticide with the exhaust gas under the tree covering. The volume of fumigant required for treating fruit trees was substantial, and generally requires vehicles for transporting the large quantity of fumigant, the hoses and the engines, which both propel the vehicles and provide the exhaust volume to fumigate trees.
Other small hand-carried or hand-propelled wheeled apparatuses for spraying fluid materials, such as DDT shown in U.S. Pat. No. 2,685,146, or other fluid materials admixed with exhaust gas and propelled through a nozzle, such as those in U.S. Pat. No. 2,655,406, as well as various other arrangements of exhaust nozzle spraying devices, such as those disclosed in U.S. Pat. Nos. 3,382,603, 3,575,349 and 4,298,167.
One portable device, as in U.S. Pat. No. 4,829,706, disclosed a two-cycle engine on an inverted bowl to inject carbon monoxide from the engine exhaust into rodent burrows. There was no suggestion of using the device for insect control or for vaporizing any insecticide. Further, there was no visible means for observing the interior of the bowl to confirm proper operation.
For purposes of tear gas dispersion, two-cycle engines have been suggested because they are lightweight, operate at high heat temperatures and have high volume exhaust discharge. In such devices, venturi action is used for drawing out liquid into a manifold for discharge via an airblower. The use of such general dispersion fogging devices has not previously been found to be effective for fire ant mound destruction, as the first small amount of disruption to the fire ant mound causes the queen to be moved through lateral passages deeper underground and thus out of reach of topically applied fumigation fogs.
In one recent patent, U.S. Pat. No. 5,154,018, the technology for high volume thermal fog generation, similar to that disclosed in U.S. Pat. Nos. 3,582,496 and 4,512,515, was employed to both obtain the high temperature generally thought to be required for vaporizing pyrethrins, such as tetramethine, cinerin and resmethrin, typically in combination with other rotenone or other pyrethrins and inert ingredients in a petroleum-based carrier typically in the range of about one part insecticide to about five to ten parts petroleum-based carrier such as diesel or fuel oil. In this apparatus, the engine drives a compressor which applies compressed air into a combustion chamber in which the fuel and insecticide mixture is combusted and then provided through a hose to a boot having a skirt therearound which is placed over the ant mounds. Because it is desirable to have high volume and high temperature, as produced by a thermal fog-generating unit, this apparatus is large, cumbersome and requires large quantities of pesticide and fuel mixture.
The treatment of treating ant mounds has also been done using pressurized thermal aerosol fog-generating devices as shown in U.S. Pat. No. 5,154,018, which disclosed the use of a boot and a flexible and plastic skirt-type covering. The device described in the '018 patent utilized high pressure, high volume fog produced from a combustible mixture of insecticide and fuel. This device required a high pressure combustion chamber, fog-generating device such that portability was not convenient. Only areas in which large vehicles carrying the fog-generator could be effectively treated for fire ants in this manner. Further, such previous devices did not contemplate the use of pesticides having the type of low toxicity as resmethrin, which is a second-generation pyrethroid pesticide and which was first manufactured in 1967.
While resmethrin has become one of the most widely used of the second-generation pyrethroids for indoor sprays and aerosols for controlling flying and crawling insects indoors, its use has not been widely adopted for killing fire ants. A topical application of the resmethrin on fire ant mounds merely resulted in temporary disruption of the mound activity. The biodegradability and the solar-degradability of resmethrin, which results within hours, would not provide a long-lasting, complete kill of the ant mound. Further, the effective use of resmethrin, which, at room temperature, is a solid, waxy substance and is not soluble in water, is dependent upon topical deposit upon the insects. In previous aerosol or other type of spray applicator, use of a solvent such as kerosene or, preferably, an inorganic carrier such as xylene, methylene chloride, isopropyl alcohol or aromatic petroleum hydrocarbons.
Other attempts to exterminate ants, such as fire ants, in subterranean colonies typically included the application of vaporized pesticides through a lance. One such lance was disclosed as a freon-and-pyrethrin-insecticide-injecting lance as disclosed in U.S. Pat. No. 4,160,336. Another lance device used liquid pesticide, such as Diazinon.TM., Malathion.TM. or Dursban.TM. liquid solutions, vaporized in the exhaust of a rolling lawnmower.
One attempt to specifically inject resmethrin into a fire ant mound with a lance was disclosed in U.S. Pat. No. 4,756,118. In this device, a heater gun with an injection nozzle lance was inserted into the mound for the application of vaporized resmethrin. The active chemical, resmethrin, was carried in a petroleum distillate in a pressurized tank on the back of the operator. The solvent and resmethrin was forced by high pressure from the tank onto a high temperature heating coil where it was vaporized. The heating coil of the heater gun operated at temperatures of about 2,000.degree. F., which according to the disclosure, was required to completely vaporize the resmethrin and petroleum distillate carrier. The vaporized resmethrin from the heating coil was injected from a nozzle in a lance, which was inserted several inches deep into the fire ant mound. The vaporized mixture permeated through the passageways of the ant mound and provided a substantially quick and complete kill of the fire ant mound. One difficulty, however, was that the apparatus was awkward, and the high temperature of the heating coil was subject to overheat and burnout unless a continuous flow of resmethrin and petroleum distillate could be maintained flowing over the heating coil in order to keep it from overheating. When moving from one mound to the next, the operator was instructed to periodically squeeze the trigger, thereby applying a stream of resmethrin and petroleum onto the heating element, and also producing a cloud of fumigate discharged into the air.
A simple, inexpensive, portable and dependable applicator for vaporizing and injecting resmethrin into fire ant mounds without the use of a lance or a pressurized spray nozzle was not previously known.